The Moog Grandmother is a semi-modular analog synthesizer that represents a significant departure for Moog Music, combining the accessibility of a keyboard-based instrument with the flexibility of modular synthesis. Despite its colorful panel and eccentric name, this is a serious and capable synthesizer that offers both beginner-friendly operation and advanced patching possibilities.

Housed in a surprisingly sturdy case reminiscent of the classic Realistic MG-1 from the late 1970s, the Grandmother measures 58 x 36.2 x 13.9 cm and weighs a substantial 7.25 kg. The instrument can function effectively without patch cables using its internal signal routing, but truly comes alive when you begin exploring its extensive patching capabilities through 41 patch points.

The synthesizer features dual oscillators derived from the Minimoog Voyager, each offering four waveforms (triangle, sawtooth, square, and pulse) with PWM capabilities. The classic 24dB/octave ladder filter is based on the vintage Moog 904a found in modular systems, providing the distinctive Moog sound with resonance maintained across the entire cutoff frequency range. A built-in spring reverb based on the Moog 905 adds spatial dimension to the sound.

The Grandmother excels as both a standalone instrument and as the centerpiece of a modular setup. Its 32-key Fatar keyboard generates velocity-sensitive CV and MIDI messages, while the comprehensive sequencer can store up to three sequences of 256 notes each. The modulation section functions more like a full-range oscillator than a traditional LFO, capable of audio-frequency modulation up to 20kHz.

What sets the Grandmother apart is its "sonic playground" philosophy - it encourages experimentation and discovery. The instrument offers six different types of portamento, extensive MIDI implementation, and the ability to process external signals. While it may appear to be an entry-level instrument due to its colorful design, it provides serious synthesis capabilities that can satisfy both newcomers and experienced synthesists.

Technical Specifications

Polyphony

• Monophonic

Sound Sources

• Oscillators: 2 analog oscillators (based on Minimoog Voyager oscillators)
• White Noise Generator: Built-in white noise source
• External Input: 1/4" TS jack for external audio processing

Oscillator Details

• Waveforms: Triangle, sawtooth, square, pulse (per oscillator)
• Pulse Width: ~16% (Osc 1), ~18% (Osc 2) duty cycle
• PWM: Available on both square and pulse waves
• Frequency Range:
  • Oscillator 1: 32' to 4' footages
  • Oscillator 2: 16' to 2' footages
• Detuning: Oscillator 2 can detune ±24 semitones
• Hard Sync: Oscillator 2 can be synced to Oscillator 1
• Linear FM: Available on Oscillator 2
• Pitch Control: CV inputs for each oscillator
• Outputs: Direct outputs for each oscillator

Velocity Sensitivity

• Key Response: Velocity-sensing keys (signal not hard-wired)
• Access: Available via MIDI and KBD VEL OUT jack
• CV Output: Analog velocity CV generation

Mixer

• Inputs: Oscillator 1, Oscillator 2, White noise generator
• Characteristics: Signal distortion above 12 o'clock, input level interaction
• Signal Types: Can mix audio signals, control voltages, or combinations

Filter (VCF - Voltage Controlled Filter)

• Type: 24dB/octave ladder filter (based on Moog 904a)
• Cutoff Range: ~11kHz (knob only), >20kHz (with CV)
• Resonance: Maintained across entire cutoff frequency range
• Keyboard Tracking: 0%, 50%, 100% rates
• Self-Oscillation: Tunable across full keyboard range
• CV Inputs: Audio signal input, contour amount input, cutoff frequency input
• Output: Patchable filter output

Static Filter (High-Pass)

• Type: 1-pole (6dB/octave) high-pass filter
• Control: Static (no voltage control)
• Access: Patchable only

Modulation Sources

• Primary: Modulation Oscillator (wide-range oscillator/modulator)
• Additional: Sample & Hold output, Envelope generator, Key tracking
• Envelope: Four-stage ADSR envelope generator
• Type: Based on Moog 902 VCA
• Gating Modes:
  • Env (envelope controlled)
  • Keyboard Release (instant attack, full sustain, envelope release)
  • Drone (always open)
• CV Input: For external control and AM synthesis
• Audio Input: Alternative audio signal input (VCA In socket)

VCA (Voltage Controlled Amplifier)

• Type: ADSR (based on Moog 911 module)
• Controls: Attack, Decay, Release knobs; Sustain slider
• Trigger Input: External trigger capability
• Outputs: Positive and negative polarity outputs

Envelope Generator

• Type: Wide-range oscillator/modulator
• Frequency Range: 0.07Hz to 1.3kHz (unpatched), up to >20kHz (with CV)
• Waveforms: Sine, sawtooth, ramp, square waves
• Destinations: Oscillator pitch, PWM, filter cutoff frequency
• Sync Input: Oscillator-style sync functionality
• Outputs: Modulation signal output, Sample & Hold output

Modulation Section (Modulation Oscillator)

Sequencer & Arpeggiator

• Type: Step sequencer and arpeggiator combined
• Mix Control: 100% dry to 100% wet
• Impact Resistance: Largely immune to physical impacts
• Routing: Can be patched anywhere in signal path
• Output: Independent rear panel output

Effects

• Spring Reverb: 6-inch spring reverb (based on Moog 905)
• Sequencer Capacity: 3 non-volatile monophonic sequences, 256 steps each
• Sequence Features: Rests, ties, legato transitions, accents
• Playback Modes: Forward, backward, random
• Transposition: Real-time sequence transposition
• Editing: Real-time sequence editing during playback

Arpeggiator Details

• Modes: As played, forward, backward, random
• Octave Range: 1, 2, or 3 octaves
• Hold Function: Key release capability
• Rate Control: Internal rate or external clock sync
• Clock Division: Selectable ppqn ratios

Utilities

• Multiple: 4 parallel-wired non-buffered patch points
• Attenuator: Bipolar attenuator (can function as DC voltage source)
• Pitch Bend: Spring-loaded pitch wheel
• Modulation Wheel: Controls hard-wired modulation amounts
• Portamento: 6 types available:
  • Linear constant time
  • Linear constant rate
  • Exponential glide
  • Each with legato on/off option
• Octave Shift: Up/down octave buttons
• Key Priority: Low-note, high-note, last-note options
• Triggering: Single triggering only

Performance Controls

Patch Points

• Total: 41 x 3.5mm patch points (front and rear panels)
• Breakdown: 21 inputs, 16 outputs, 4-jack parallel multiple
• Compatibility: Eurorack voltage levels (±5V standard)

CV Outputs

• Gate Out: Keyboard/arpeggiator/sequencer gate signals
• KB Out: Pitch CV from keyboard/arpeggiator/sequencer
• KB Vel Out: Velocity CV and accent CV

Audio Connections

• Main Output: 1/4" jack (line/headphone combination, unbalanced/TRS)
• Eurorack Output: 3.5mm jack (±5V range)
• Reverb Output: 3.5mm jack (independent spring reverb output)
• Audio Input: 1/4" jack (high-gain, unbalanced, feeds directly to mixer)

Clock & Sync

• Clock Input: External clock or step trigger
• Start/Stop Input: Remote transport control
• Reset Input: Sequence/arpeggiator reset
• Clock Output: Internal clock output

MIDI Implementation

• Connections: 5-pin DIN In/Out/Thru, USB MIDI In/Out
• Features: Extensive MIDI CC implementation
• Sustain Pedal: MIDI sustain pedal support
• Control: Various synthesis parameters via MIDI CC

Utilities

• Multiple: 4-way passive multiple
• Attenuator: Bipolar attenuator (can function as DC voltage source)

Calibration

• Digital Control: Internal digital electronics for pitch interpretation
• Calibration: Undocumented calibration/reset commands available
• Global Parameters: Various synthesis parameters controllable via MIDI

Additional Features

• Sound Engine: Fully analog
• External Processing: Can process external audio signals through internal signal path
• Modular Integration: Fully compatible with Mother-32, DFAM, and other modular systems
• Eurorack Compatibility: Standard Eurorack voltage levels and patch point spacing

Keyboard

• 32 full-size keys (Fatar keybed)
• Velocity sensitivity

Physical Dimensions & Build

• Dimensions: 58.42 x 36.19 x 13.97 cm (23" x 14.25" x 5.5") (W x D x H)
• Weight: 7.25 kg (16 lbs)
• Construction: Sturdy case design based on Realistic MG-1 recreation

Power

• Supply: Included 12V DC power adapter (positive tip)
• Rating: 2A, 100-240V AC, 50/60Hz
• Connector: Barrel connector (no locking mechanism)
• Consumption: Not specified in review